Vista Dual Boot Black Screen

I have this post on How To Geek forum and the Windows Vista Forum, but no luck. Thought I'd try here. And I hope there is no rule against long posts, if there is I'm sorry.

I'm running a GQ5140 desktop from frys (I know it's not the best rig) with a Celeron D processor, 1.5 gb of ram, I have a eGeForce 7200 GS, 80gb internal harddrive, 500gb WD external drive, a CD RW/DVD Rom, with Vista Home Basic. Even though it doesn't have the best specs, it runs my older games and I can even play Ovlivion on it with out too much trouble. I haven't had many problems with it before.
Just recently I really wanted to play Assassins Creed, and I noticed I would have to upgragde my Ram if i tried to play it on Vista. But on Xp it only needs 1gb of ram to play. So i decided to take my Xp Pro disk from my older computer and install it beside Vista. I partitioned my external drive (I decided to give Xp about 80gb), I installed EasyBCD (I might have done this too early, the info i had said to install it after I installed my other OS and repaired Vista). I read all the warnings about how Vista doesnt like dual booting and all that stuff, but me being the stupid person I am decided that I wasn't going to have any problems. And so i restarted my computer and booted from the Xp disk. I told it to install it on my X: drive (what i decided to name it) and it seemed to go through the setup fine. After the setup it rebooted and the Bios information came up as per usual (I guess it's called the POST screen or something). It then went into a black screen and it said something along the lines of "OS cant be started" or something like that. I thought that was odd, so i C+A+D and told it to boot from the Xp disk again. I went through setup again, except this time it game me a warning about installing two OS on the same drive (I told it to install on the x drive again so i guess xp was already on it) but i didnt think it would be a problem because it was the same OS on the X drive. It seemed to go through setup fine again, although it seemed faster this time but i just attributed that to the fact that it already had all the files on it. Rebooted, the POST screen came up, but now it just gives me a black screen with the dreaded white blinking dash. I can C+A+D to reset, and I can enter the setup for the bios and I can choose what drive to boot from, but no matter what drive I boot from it gives me the black screen. I cant even run a system restore from my factory disk, which REALLY worrys me. I have my external drive unplugged now (which is where Xp was installed) and I cant boot from my Internal HDD or my DVD drive which has the recovery disk it it. I can't even boot into DOS or safe mode to change my boot parameters to (rd=disk0s1) which is what some other website told me to do. Unless there's a way to enter boot parameters into a BIOS setup, or reset my bios or something, I really have no idea what to do. Please help me. Frys was no use, and I really need my computer back. Thanks so much in advance. (srry for the long post)